Luminescent Security Elements Using Joint Emission Bands

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Solution Overview

Problem

Existing security elements for value documents using luminescent substances are limited in their ability to distinguish between different substances due to their limited number of spectral lines and overlapping emissions, restricting the variety of distinguishable elements and increasing the risk of forgery.

Innovation Solution

The use of at least two luminescent substances with a joint emission band but distinct excitation bands allows for differentiation, enabling the integration of previously indistinguishable substances and enhancing security through unique encoding possibilities.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If traditional luminescent substances with distinct emission bands are used, then reliable detection and delimitation is achieved, but the number of distinguishable security elements is limited

Engineering Contradiction:

Improvedetection reliabilityVSAvoidvariety of distinguishable elements

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent changes the detection parameter from emission wavelength to excitation wavelength. By using substances with identical emission bands but different excitation bands, the system can distinguish between multiple luminescent substances without spectral overlap in emission, thereby increasing the variety of distinguishable security elements while maintaining detection reliability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent transitions from one-dimensional spectral differentiation (emission wavelengths) to two-dimensional spectral characterization by incorporating both excitation and emission bands. This dimensional expansion allows for significantly more distinguishable combinations of luminescent substances, solving the limitation of variety while preserving detection precision

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Adaptability or versatility

If multiple luminophores are combined to increase variety, then more encodings are possible, but emission overlaps make discrimination difficult

Engineering Contradiction:

Improvenumber of encodingsVSAvoiddiscrimination difficulty

Core Design Contradiction:

Adaptability or versatilityVSDifficulty of detecting and measuring

Solution Approach 1:

The patent segments the spectral characteristics into separate excitation and emission components. By assigning different excitation bands to different luminescent substances while allowing identical emission bands, the system enables clear discrimination of individual substances even when emissions overlap, thus facilitating combination of multiple luminophores for increased encoding variety

Inventive Principle:

Principle #1Segmentation

3Reliability

If luminescent substances with predictable emission wavelengths are used, then reliable identification is achieved, but the number of suitable ions is limited

Engineering Contradiction:

Improveidentification reliabilityVSAvoidnumber of available ions

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent inverts the traditional approach by using excitation wavelengths instead of emission wavelengths for identification. This inversion expands the pool of usable luminescent substances because excitation bands can be more easily differentiated across various ion types, thereby increasing the quantity of available substances while maintaining reliable identification

Inventive Principle:

Principle #13The other way round (Inversion)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach significantly increases the variety of distinguishable security elements, providing enhanced protection against forgery by allowing for multiple encodings and improved verification methods through selective excitation wavelengths.

Implementation Method 1

at least two luminescent substances, wherein the security element has a first and a second luminescent substance which have a substantially identical, joint emission band, wherein at least the first or the second luminescent substance, or both luminescent substances, have at least one excitation band that leads to an emission at the joint emission band

Methodology Applied

Scientific EffectLuminescence: Luminescence

Implementation Method 2

The emission of the employed luminophores is also referred to as luminescence, which may involve fluorescence and/or phosphorescence

Methodology Applied

Scientific EffectFluorescence: Fluorescence

Implementation Method 3

Combinations of transition metals and/or rare earth metals have also been discussed. Such substances have the advantage that, in addition to the above-mentioned luminescences, there are observed so-called energy transfer processes which can lead to complicated spectra. In such energy transfer processes an ion can transfer its energy to another ion

Methodology Applied

Scientific EffectEnergy transfer:

Data Source

PatentUS9987874B2Authenticity feature in the form of luminescent substances

Publication Date: 2018.06.05 GIESECKE & DEVRIENT CURRENCY TECHNOLOGY GMBH

AI summary

A security element has at least two luminescent substances, in which the security element has a first and a second luminescent substance which have a substantially identical, joint emission band. The first or the second luminescent substance, or both luminescent substances, have at least one excitation band that leads to an emission at the joint emission band only in the case of the first or the second luminescent substance.